Professional imaging systems, such as those employed for medical diagnostic (radiological) applications, having historically captured and recorded images on relatively large sized sheets of photosensitive material, using large volume wet development equipment. With the recent enactment and more rigid enforcement of environmental regulations that require safeguards against exposure to and proper disposal of chemicals used in image development equipment, image processing providers have begun the replacement of these cumbersome and expensive wet-development systems with dry silver processes. For example, in a typical dry silver imaging application for medical diagnostic applications, such as a sonogram or X-ray, the image of interest may be electro-optically captured on a 20.3 cm.times.25.4 cm (8".times.10") sheet of dry silver photosensitive medium, so that the image size is large enough to be viewed and analyzed, is readily physically accommodated within the patient's file, and may be easily handled and stored by medical personnel without exposure to wet chemicals.
In the course of operation of a dry silver process-based imaging system, just as in the use of relatively small hand-held cameras, it is necessary to store the individual frames of the photosensitive media in a light-tight housing, while affording ready access to the frames as they are needed by the imaging equipment. In hand-held cameras, the film packaging is relatively compact, with the film being configured as either a continuous multi-frame roll housed in a light-tight cylindrical canister, or as individual sheets that may be housed in an auto-feed sealed cartridge that is disposable after all of the film sheets have been used. Unfortunately, due to their configuration and small size, neither of these hand-held camera film storage and feed approaches is capable of storing larger sheets of photosensitive material and interfacing such media with the sheet or web advance mechanisms employed by the larger, diagnostic imaging equipment.
Light-tight, single-use containers or packages for larger photosensitive materials used in, for example, medical diagnostic applications are generally known. As shown in U.S. Pat. No. 4,860,042, these light-tight containers can include a film bag or a tray covered by a lid. Also shown are carriages, or holders, which mate with the main body of a film loading device and remove the cover or the film bag while maintaining light-tightness.
Containers for larger photosensitive materials have been designed to function with vacuum or suction feeding mechanisms within an imaging unit. This type of feeding mechanism, which lifts individual sheets of the photosensitive materials from the container and insert them into the imaging station of the imaging unit, requires a vacuum system as well as numerous parts for lifting and inserting the sheets. In addition, this type of feeding system can be susceptible to feeding multiple, rather than individual, sheets which are stuck or blocked together which can adversely affect the imaging process.
In addition, there has recently been developed a kick-feed mechanism for delivering larger photosensitive material wherein the sheets are moved by friction, rather than a vacuum or suction. One example of such a mechanism is shown in co-pending U.S. patent application Ser. No. 08/344,462, filed Nov. 23, 1994, entitled "IMAGING UNIT CONTAINER HAVING SHIFTABLE WALLS". With such a kick-feed mechanism for larger sheets of photosensitive material, problems may develop in the feeding of the sheets of photosensitive material if there is not a proper coefficient of friction relationship between the drive roller, sheets of photosensitive material, liner, and container base. The present invention addresses these concerns and provides for the aforementioned components all having a coefficient of friction which provides for an improved sheet feed apparatus for an imaging device.